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41dB Step RF Attenuator


Qrpers love to operate with low power, and one of the things that they love to do is see how low in power they can go and still make a contact. The easiest way to do this is with an attenuator. Cut your power by 3dB, and you cut it in half. Start with 1 Watt, switch the attenuator inline with 3dB, and you now are at 0.5 Watts output. All with just the flip of a switch. The problem has been that the commercially available attenuators are expensive if you want them to take 5 Watts. We have developed a kit that is functional and affordable, and comes with a custom designed case that you will be proud to have on your bench.

We used the attenuator circuit in the ARRL handbook, and Ken LoCasale, WA4MNT, designed a case to package it in that would make the kit easy to build. The case is prepunched, and all parts are included, including a commercial quality double sided, silkscreened, soldermasked pc board. The connectors are BNC's, and it is bi-directional.

The prototype was tested on an Agilent PNA E8357A Network Analyzer. We found that it was accurate to within 1-2% typically. We were very pleased with this accuracy, and feel that it is typical. Your accuracy will depend on your building skills and the parts used, but should be very close to what we obtained.

One use of an Attenuator is to work contacts for the ARCI Thousand miles per watt award. Now, if you work someone 500 miles away and are running 1 Watt, all you have to do to earn the award is to use the attenuator with 3 dB of attenuation, and you will effectively have had a 1000 mpWatt contact, because you have used Watt to travel 500 miles. It is a lot of fun to chase those awards, and see if you can break records that have been kept by ARCI.

The cost of the Attenuator is $50 plus shipping and handling. Kits are in stock and ready to ship. Enjoy.

Supporting Files and Documents

 Attenuator Assembly Manual

Page last updated: 02/28/2015, 16:01:28
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